I had a 301, the top of the line unit, and would not buy one again.
Battery life was pretty poor... 8 hours. My color GPS (Garmin Legend C) that I have now gets 3 times that.
Durable? Sure. All Garmin GPSs are solid, though.
My beefs with it:
1. No mapping etc, made it useless for anything except hiking imo
2. It wasn't very useful for hiking because the small patch antenna made getting a fix under tree cover very difficult
3. I connected it to my laptop in my car, but this was a major hassle. It was awkward to view and set-up. It works better in theroy than it does in practice.
4. The interface sucks imo. You cannot pan the map screen. Not really sure what they were thinking there.
The Garmin Legend C is a *LOT* better and well worth the additional price. The color screen is fantastic and it's great for car navigation, and the 3x battery life and larger patch antenna make it better for hiking as well. (especially since you can use topo maps)
I would not buy a Geko again. It wasn't bad per se... but very limiting.
I also did not think the sensors were worth the additional price, since I brought a magnetic compass anyway. But YMMV.